Magnetically controlled thermal relay

ABSTRACT

An adjustable thermal relay for use in electric blankets, electric hair driers or electric room temperature controllers is provided with an exciting coil provided close to the reverse side of the surface of a moving contact plate of magnetic material, to induce a continuous magnetic force for attracting said moving contact plate. By increasing the exciting current in the exciting coil, a gap between a moving contact and a fixed contact is widened and therefore, the operating temperature at which the contacts of the thermal relay are switched on or off changes.

United States Patent [72] Inventor Koichi Yosbimura Kadoma, Japan [2]] Appl. No. 22,015

[22] Filed Mar. 23, 1970 [45] Patented Jan. 4, 1972 [73] Assignee Matsushita Electric Industrial Co., Ltd.

Osaka-fu, Japan [32] Priorities Oct. 16, 1967 [33] Japan Oct. 16, 1967, Japan, No. 42167091; Oct. 16, 1967, Japan, No. 42/67092; Feb. 6, 1968, Japan, No. 43/8142; Feb. 6, 1968, Japan, No. 43/8143; Feb. 7, 1968, Japan, No. 43/9297; Feb. 12, 1968, Japan, No. 43/ 10720 Original application Oct. 15, 1968, Ser. No. 767,710, now abandoned. Divided and this application Mar. 23, 1970, Ser. No. 22,015

[5 4] MAGNETICALLY CONTROLLED THERMAL RELAY 5 Claims, 13 Drawing Figs.

[52] US. Cl 337/366, 335/145 [51] Int. Cl H01h 37/52,

HOlh 37/66 Primary ExaminerBernard A. Gilheany Assistant ExaminerDewitt M. Morgan Attorney-Wenderoth, Lind & Ponack ABSTRACT: An adjustable thermal relay for use in electric blankets, electric hair driers or electric room temperature controllers is provided with an exciting coil provided close to the reverse side of the surface of a moving contact plate of magnetic material, to induce a continuous magnetic force for attracting said moving contact plate. By increasing the exciting current in the exciting coil, a gap between a moving contact and a fixed contact is widened and therefore, the operating temperature at which the contacts of the thermal relay are switched on or off changes.

PATENTEUJAN ma 31633143 SHEET 1 OF 3 A K 3/, x 3 4 FIGI IO 6 I L W 39 8 37 FIGS MOTIVE TEMPERATURE EXCITING CURRENT FIGA INVENTOR KOICHI YOSHIMURA BY 2M ATTORNEYS PATENTEUJAN 4m 31633143 SHEET 2 OF 3 FIGB LL] [1: D & ON if LIJ ,I v O E v 70% T L I EXCITING CURRENT MOTIVE TEMPERATURE o 5 8 8 8 I INVENTOR KOICHI YOSHIMURA SOITIA IOOmA EXCITING CURRENT F169 I BY @gM ATTORNEYS PATENTEDJAN M972 3,633,143

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1 1 A MAGNETICALLY CONTROLLED THERMAL RELAY This application is a division-of my copending application Ser. No. 767,710, filed-Oct. 15, 1.968 and now abandoned.

BACKGROUND .OF THE INVENTION ing mechanical'contact gapadjusting means,remote control of the setting of the temperature is not practical, and hence, accurate control of the gapcan not be obtained.

SUMMARY OF THE INVENTION This invention relates totherrnal relays which have been improved to eliminate the shortcomings of conventional thermal relays by providing near the moving contact plate and/or fixed contact plate an exciting coil for supplying electromagnetic force thereto. Thismakes possible electromagnetic control of the operating temperature, i.e., the preset temperature at which thecontacts switch on or off, by changing the standard position of said moving contact plate by adjusting the exciting current of said exciting coil.

Therefore, one object of the present invention is to provide I a novel thermal relay in'which the operating temperature can be remotely controlled by controlling electromagnetic means.

A further object of the present invention is to provide a novel thermal relay in which continuous and stable control of the operating temperature over awide temperature range can be carried out by adjusting the exciting current in an exciting coil.

BRIEF EXPLANATION OFTI-IE DRAWINGS Other features anddetails of the present invention will be set forth in the following detailed description, taken with the accompanying drawings, in which:

FIG. 1 is a partial sectional side elevation view and circuit diagram of an electromagnetically controlled thermal relay according to this invention;

FIG. 2 is an equivalent circuitdiagram corresponding to the construction of the thermal relay shown in FIG. 1;

FIG. 3 is a partial sectional side elevation view and circuit diagram of another electromagnetically controlled thermal relay according to this invention;

FIG. 4 is a graph showingthe characteristics of the thermal relay shown in FIG. 3;

FIGS. 5 and 6 are partial sectional side elevation view of other electromagnetically controlled thermal relays according to the present invention;

FIG. 7 is a graph showing the characteristics of the thermal relays of FIGS. 5 and 6;

FIG. 8 is apartial sectional side elevation view of another electromagnetically controlled thermal relay according to the present invention;

FIG. 9 is a graph showing the characteristics of the thermal relay shownin FIG. 8;

FIG. 10 is a partial sectional side elevation view of another electromagnetically controlled thermal relay according to the present invention;

FIG. 11 is a graph showing the characteristics of the thermal relay shown in FIG. 10; and

FIGS. 12 and 13, are partial-sectional side elevation views of still other electromagnetically controlled thermal relays according'to the present invention.

DETAILED DESCRIPTION In FIG. 1, there is shown a relay according to the invention comprising a fixed contact plate 1 made of electrically conductive, magnetic material. Insulator 2 is mounted on .the upper surface of the end of the fixed contact plate 1. A fixed contact 3, preferably of magnetic material, is mounted on the central part of the insulator 2. An exciting coil-4 is-wound around the fixed contact 3, and the lead wires 5 andi6 of said exciting coil 4 are connected to said fixed contact plate 1 and to said fixed contact '3, respectively. A moving contact bimetallic plate8, which is also electrically conductive and magnetic, is provided with a moving contact 7 on the lower surface of its free end, opposite said fixed contact 3. The moving contact plate8 and the fixed contact plate 1 are mechanically connected to and electrically insulated from each other by insulator 9 mounted between the supported ends of said moving contact plate8 and fixed contact plate I. A load 10, for instance, a heater wire of anelectric'blanket or an exciting coil of an electromagnetic valve, has one end connected to said fixed contact plate 1. Between the fixed end of the moving contact 8 and the other end of said load 10 is connected an alternating current power source 11.

In the operation of the thermal relayit is seen that the moving contact plate 8 bends in response to ambient temperature change, and consequently the moving contact 7-contacts or separates from the fixed contact 3, respectively. At the moment when the contacts 3 and7 comeinto contact with each other, sparking is suppressed due to he equivalent electrical lengthening of the gap between the contacts 3 and 7, due to the strong magnetic field, such asseveral hundred to'several thousand oersteds, produced at that moment by the current flowing through the exciting coil 4. The operating temperature of the thermal relay, defined as the temperatureat which a set of contacts switch on or off, depends only upon the bending of the bimetallic plate 8 when the contacts Sand 7 are touching each other. However, when contacts 3 and 7 are tending to separate from each other, the existence of the exciting current in the coil 4 and the magnetic flux flowing through each of contacts 3 and 7 produces an attracting force between the contacts 3 and 7, tending to maintain the contacts closed.

On account of this attracting force, the position of contact 3 does not change, and hence there is a delay in separation of contacts 3 and 7, depending on the intensity of said exciting current. Accordingly, by changing said exciting current, adjustment of said delay, and hence, adjustment of said operating temperature of the thermal relay can be performed.

Because of the connection of said exciting coil 4 between the fixed contact 3 and the fixed contact plate 1, the magnetic flux diminishes to zero as soon as the contacts 3 and 7 open, allowing the motion of moving contact plate 8 to be free from the influences of said magnetic flux, and thereby resulting in quick detaching of contacts 3 and 7.

FIG. 2 shows an equivalent circuit corresponding to the above-mentioned thermal relay circuit shown in FIG. 1 showing by corresponding reference numerals the elements thereof.

As is set forth above, the thermal relay of FIG. 1 and FIG. 2 can have the operating temperature and the differential tem perature, i.e., the temperature difference between the off and on temperatures, adjusted, and moreover, the contacts open with a satisfactory snap action.

Referring now to FIG. 3, there is shown a fixed contact'plate 31 made of electrically conductive and magnetic material, and having a fixed contact 32 mounted on the free end thereof. A moving contact plate 34 made of a bimetallicplate, which is also electrically conductive and of magnetic material, is provided with a moving contact 33 mounted on its free end. An insulator piece 35 mechanically connects the supported ends of said moving contact plate 34 and the fixed contact plate 31. Around said insulating piece 35. and between the fixed contact plate 31 and moving contact plate 34 is. positioned an exciting coil 36. A variable resistor 37 is connected at one end to one lead wire of said exciting, coil 36. A load 38 is connected between the other end of said variable resistor 37 and said fixed contact plate 31. Said moving contact plate 34 and the other lead wire of said exciting coil 36 are commonly connected to one end of an alternating current power source 39, to the other end of which is connected the junction of said variable resistor 37 and said load 36.

The exciting coil 36 produces magnetic flux composed of a main fiux flowing in a flux circuit consisting of insulator 35, moving contact plate 34, moving contact 33, fixed contact 32, fixed contact plate 31, and insulator 35, and of a leakage flux The main flux M, which flows through the contacts 32 and 33, can be greatly increased by employing silver-nickel (Ag- Ni) alloys for said contacts 32 and 33.

By its operation, it is seen that the moving contact plate 34 bends in response to the ambient temperature changes, and consequently, the moving contact 33 contacts or separates from the fixed contact 32. In the thermal relay of FIG. 3, the operating temperature increases in accordance with the increase of exciting current of the coil 36, as shown in FIG. 4, where temperature T is the operating temperature for an exciting current of zero when contacts 32 and 33 contact and open.

In the thermal relay of this construction, because contacts 32 and 33 break from each other with a rise of temperature, the operating temperature can be increased gradually by gradually decreasing the resistivity of the variable resistor 37. Therefore, by a scale (not shown) on the knob of said variable resistor 37, a setting of the desired operating temperature of said thermal relay can readily be carried out.

The thermal relay of this example can have the operating temperature remotely set by adjusting the current in the exciting coil.

In FIG. there is shown a caulking rivet 41 and an insulating sleeve 42. Insulating washers 43, 47, and 55 on sleeve 42 are made of synthetic resin with or without filling material, e.g., glass powder or ceramic powder. A fixed contact plate 44 has its supported end mounted between said insulating washers 43 and 47. A fixed contact 45 having a contacting face 45a is mounted at the free end of the fixed contact plate 44. A terminal 46 is electrically connected to said fixed contact plate 44 and is interposed between washer 47 and plate 44. The other terminal 48 is electrically connected to a bimetallic plate 49 and is interposed between washer 47 and bimetal plate 49.

of the operating temperature of this thermal relay is also proportional to said change in position of the bimetallic plate. Therefore, if the moving contact 50 is made to contact the fixed contact 45a at a high temperature and to separate from the fixed contact 45a at a low temperature, the relationship between the exciting current of the exciting coil 52 and operating temperature of this thermal relay becomes as shown in FIG. 7. In FIG. 7, a line marked ON indicates the characteristic when the contact 50 touches the face 45a of the contact 45, while the other line marked OFF indicates that when the contact 50 separates from the contact 45.

As is explained above, the thermal relay of this example is constructed so as to make it possible to change electromag- A moving contact is mounted at the free end of said bimetallic plate 49 opposed to said contacting face 45a of the moving contact 45. A magnetic material piece 51 is mounted at the middle part of the bimetallic plate 49. An exciting coil 52 is wound around said caulking rivet 41, as shown. A magnetic material plate 53 is mounted parallel with said bimetallic plate 49. An elastic piece 54, for instance, of rubber, vinyl chloride, or an insulated spring, is mounted between said magnetic material piece 51 and magnetic material plate 53. Mounted between said insulating washers 47 and 55 are terminal 48, the supported end of said bimetallic plate 49, the exciting coil 52 and the supported end of said magnetic material plate 53.

The normal position of said bimetallic plate 49 can be easily changed in this example of the thermal relay of the invention by changing the current flowing through said exciting coil 52.

Namely, in this example, magnetic flux is produced by passing a current of predetermined intensity through said exciting coil 52. The flux circuit is created through magnetic material plate 53, magnetic material piece 51, bimetallic plate 49, and back to magnetic material plate 53. Due to the magnetic flux, the magnetic material piece 51 is attracted to the magnetic material plate 53, thereby causing the bimetallic plate 49 to change its position, as shown by the broken lines in FIG. 5, from its standard or normal position. The extend of said change is substantially proportional to the intensity of the current in the exciting coil 52. On the other hand, the change netically the normal standard position of the bimetallic plate, thereby enabling remote control of said standard position with lasting reliability.

A caulking rivet 61 is shown in FIG. 6 having an insulating sleeve 62, for instance, of glass or synthetic resin. A bimetallic plate 63 has its supported end around the insulating sleeve 62, while its free or moving end 63a is bent upwardly. An insulating holder 64 made of paperboard or synthetic resin or the like is mounted on said bent moving end 63a of the bimetallic plate 63. A moving contact plate 67 has a moving end 67a inserted in and held in an opening in said insulating holder 64, while its supported end is around the middle part of the insulating sleeve 62. A moving contact 68 is mounted near the moving end 670 of the moving contact plate 67. A fixed contact 72 is mounted at or near the end of a fixed contact plate 71 having its fixed end around insulating sleeve 62. A magnetic material plate 73 made of iron, silicon steel, or the like, is rivetted to said end of the fixed contact plate 71 by means of fixed contact 72. A supporting yoke 75 made of iron, silicon steel, or the like, has its supported end fixed around the upper end of said insulating sleeve 62. A pole piece 76 is mounted in the center part of an L-shaped yoke 760 on the end of said supporting yoke 75. An exciting coil 78 is wound on a bobbin 77 fixed on said pole piece 76. An elastic piece 79, for instance, rubber, vinyl-chloride, or the like, is mounted between the lower surface of said pole piece 76 and the magnetic material plate 73. Insulating washers 65, 69, 74, 60, and 60' hold bimetallic plate 63, moving contact plate 67, fixed contact plate 71 and supporting yoke 75 together on said sleeve 62 in such a way that the contacts 68 and 72 are opposite to each other. Terminals 66 and 70 are electrically connected to moving contact plate 67 and fixed contact plate 71, respectively, as shown.

The thermal relay of this example is constructed so that the position of the fixed contact plate 71 can be changed, and hence the position of fixed contact 72, by attracting the magnetic material plate 73 upwards toward the pole piece 76, by fiow of current in the exiting coil 78. Consequently depending on the intensity of the current in the exciting coil 78, the upward displacement of the fixed contact plate 71 towards the pole piece 76 increases. Therefore, if the moving contact 68 is made to contact the fixed contact 72 at a high temperature and to separate from the fixed contact 72 at a low temperature, the relationship between the exciting current of the exciting coil 78 and operating temperature of this thermal relay becomes as shown in FIG. 7.

As explained above, the thermal relay of this example can be operated to readily adjust the operating temperature, thus enabling the operating temperature to be remotely controlled by controlling the exciting current. This is because the position of the fixed contact 72, opposite the moving contact on the bimetallic plate, can be electromagnetically changed.

In FIG. 8 there is shown a fixed contact plate 81 having fixed contact 82 near its free end. A bimetallic plate 83 is positioned opposite this fixed contact plate 81 and has a moving rivet contact 88 at its free end. A supporting yoke 84 is fixed opposite the bimetallic plate 83 and mounted at its free end is an electromagnet 85. A magnetic material plate 86 is mounted opposite the electromagnet 85 at the free end of the bimetallic plate 83 by rivet contact 88. The supporting yoke 84, the

bimetallic plate 83, andthe contact plate 81 are positioned at certain distancesby a caulking metal rivet 89, an insulating sleeve 90 on the rivet 89, andinsulating spacers 91. The bimetallic plate 83 and the fixed contact plate 81 are connected electrically by an external circuit through terminal contacts 92 and 93, respectively.

When exciting current which flows through the electromagnet 85 becomes sufficiently large, the bimetallicplate 83 having magnetic material plate 86 thereon is strongly attracted by the electromagnet 85 and inhibitscontacts 82 and 88 from contacting each other in the ON position. Therefore, if the moving contact 88-is made to contact the fixed contact 82 at a low temperature and to separate from the fixed contact 82 at a high temperature, the relationship between the exciting current of the electromagnet 85 and operating temperature of this thermal relay become as shown in FIG. 9.

Thus, because it is possible to control at will the operating temperature of the bimetallic plate by adjusting the exciting current which flows in the electromagnet 85, remote control of the operating temperature is quite easy, and also it is possible to control the operating temperature with a comparatively high degree of precision.

Thus, this example eliminates the conventional shortcomings described above, and is especially efi'ective for remote control by electromagnetically adjusting the gap between the contacts.

In FIG. is shown a fixed contact plat 101 having near its end an electromagnet 102 and a fixed contact 103 threadedly attached to an intermediate part of the fixed contact plate 101. A bimetallic plate 104 is mounted opposite the contact plate 101 and has at its free end a magnetic material plate 105 opposite the electromagnet 102, and to which plate 104 there is attached near the free end a moving contact 106. The supported end of the bimetallic plate 104 and that of the fixed contact plate 101 are mounted on a caulking metal rivet 108 having an insulating sleeve 109 therearound and insulating spacers 110 therein. The bimetallic plate l04-and the fixed contact plate 101 are connected by an external circuit through terminal connectionslll and 112, respectively.

Excitation of the above-mentioned electromagnet 102 suppresses the movement of the bimetallic plate 104 away from the fixed contact plate 101. Namely, when the exciting current in the electromagnet 102 becomes sufficiently large, the bimetallic plate 104 is strongly attracted to the electromagnet 102, and consequently, in order for contacts 103 and 106 to separate to the OFF condition, the temperature around the bimetallic plate 104 must become quite high. FIG. 11 shows the characteristic of the exciting current flowing into the electromagnet 102 and the operating temperature for. opening and closing the contacts 103 and 106. In FIG. 11, the curve marked OFF indicates the operating temperature when the contacts 103 and 106 are opened, and the curve marked ON indicates the operating temperature when the contacts 103 and 106 close.

In FIG. 12 is shown a hermetically sealed cylindrical capsule 121 of nonmagnetic material having therein a moving contact plate 122 made of bimetallic magnetic materials, the outer end part of which is fixed to an end wall of the capsule 121, with the end projecting slightly outside the capsule 121. A fixed contact plate 123 made of magnetic material has its underside substantially touching the inside bottom of the capsule 121, and has an outer end part fixed to the other end wall of the capsule 121 with the end projecting slightly outside the capsule. An exciting coil 124 is wound around the cylindrical wall of the capsule 121. Moving contact 125 and fixed contact 126, respectively, are mounted opposite each other at the inner free ends of the moving contact plate 122 and the fixed contact plate 123. This device makes the moving plate 122 bend when the temperature risesso as to open the contacts 125 and 126, and make them revert to the former closed condition when the temperature falls. In this case, if a current is passed through the exciting coil 124, a magnetic flux flows through the contacts l25and 126, as shown in the drawings,

and as a result, a correspondingly high operating temperature is required to open the contacts -and 126. In other words, by varying the current flowing in the exciting coil 124, it-is possible to vary the operating. temperature to open and closev the contacts 125 and 126. The relationships betweenthe current passing through the exciting coil 124 and the operating temperature required to open and close the contacts 125 and 126 are found to be the same as those shown in FIG. 4.

As contact materials for construction of contacts 125 and 126, such magnetic materials as Ag-Ni alloys produce good effects.

In FIG. 13, on the other hand, a cylindrical bobbin 131 having flanges on the ends is'wound with an exciting coil 134. A moving contact plate 132 and a fixed contact plate 133 areenclosed in the space inside the bobbin 131. Terminals plates 137 and 138 are attached to the opposite ends of the bobbin 131 for hermetically sealing the space within the bobbin. The ends of moving contact plate 132 and fixed contact plate 133 project through the terminal plates 137 and 138, respectively. Said moving plate 132 is constructed of a bimetallic material, as suggested above in FIG. 12. The space within the bobbin 131 can be evacuated or filled with a gas depending on the necessity of protecting the surfaces of the terminals from adverse changes.

With the present invention, as explained above, since opening and closing movements of the contacts 135 and 136 can be regulated by varying the current intensity of the exciting coil 134, remote control is easy. Furthermore, since the contacts are hermetically sealed inside the capsule, they are kept free from dust and dirt. Moreover, by evacuating the inside of the capsule or filling it with a gas, the surfaces of the terminals can be maintained in an unchanged condition, enabling them to perform stable switching operations.

What is claimed is:

1. A magnetically controlled thermal switch comprising a pair of contact plates each having a contact, said contacts positioned to oppose each other with a specified gap therebetween, a first of said contact plates being composed of a bimetal bendable upon temperature change to move the contact thereof with respect to the contact of the other of said contact plates, and a second of said contact plates composed of magnetic material; and means for inducing a magnetic force regardless of whether said contacts are opened or closed tending to cause one of said contact plates to move in such a direction to vary said gap, said means including an exciting coil means positioned adjacent said one contact plate on the side thereof opposite the other of said contact plates, said-exciting coil means being part of a magnetic circuit resulting in the formation of said magnetic force.

2. A switch as claimed in claim 1, wherein said first contact plate is said one contact plate, and further comprising a magnetic material piece mounted on said first contact plateanda magnetic material plate spaced from said magnetic material piece, and said coil means is positioned between said magnetic material piece and said magnetic material plate such that said magnetic circuit is created through said magnetic material plate, said magnetic material piece, said contact plate, and back to said magnetic material plate.

3. A switch as claimed in claim 1, wherein said second contact plate is said one contact plate, and further comprising a magnetic material plate positioned on said one contact plate, such that said magnetic circuit is created through said magnetic material plate.

4. A switch as claimed in claim 3, further comprising a supporting yoke positioned on saidside of said one contact plate,-

and wherein said exciting coil means is mounted on saidsupporting yoke.

5. A switch as claimed in claim 1, further comprising a supporting yoke positioned on said side of said one contact plate, and a magnetic material plate positioned on said one contact plate, wherein said first contact plate is said one contact plate, said exciting coil means is mounted on said supporting yoke and said magnetic circuit is created through said magnetic material plate.

t if 

1. A magnetically controlled thermal switch comprising a pair of contact plates each having a contact, said contacts positioned to oppose each other with a specified gap therebetween, a first of said contact plates being composed of a bimetal bendable upon temperature change to move the contact thereof with respect to the contact of the other of said contact plates, and a second of said contact plates composed of magnetic material; and means for inducing a magnetic force regardless of whether said contacts are opened or closed tending to cause one of said contact plates to move in such a direction to vary said gap, said means including an exciting coil means positioned adjacent said one contact plate on the side thereof opposite the other of said contact plates, said exciting coil means being part of a magnetic circuit resulting in the formation of said magnetic force.
 2. A switch as claimed in claim 1, wherein said first contact plate is said one contact plate, and further comprising a magnetic material piece mounted on said first contact plate and a magnetic material plate spaced from said magnetic material piece, and said coil means is positioned between said magnetic material piece and said magnetic material plate such that said magnetic circuit is created through said magnetic material plate, said magnetic material piece, said contact plate, and back to said magnetic material plate.
 3. A switch as claimed in claim 1, wherein said second contact plate is said one contact plate, and further comprising a magnetic material plate positioned on said one contact plate, such that said magnetic circuit is created through said magnetic material plate.
 4. A switch as claimed in claim 3, further comprising a supporting yoke positioned on said side of said one contact plate, and wherein said exciting coil means is mounted on said supporting yoke.
 5. A switch as claimed in claim 1, further comprising a supporting yoke positioned on said side of said one contact plate, and a magnetic material plate positioned on said one contact plate, wherein said first contact plate is said one contact plate, said exciting coil means is mounted on said supporting yoke and said magnetic circuit is created through said magnetic material plate. 